Poly(ADP-ribosyl)ation (PARylation) is a specific form of post-translational modification (PTM) predominantly triggered by the activation of poly-ADP-ribose polymerase 1 (PARP1). However, the role and mechanism of PARylation in the advancement of acute kidney injury (AKI) remain undetermined. Here, we demonstrated the significant upregulation of PARP1 and its associated PARylation in murine models of AKI, consistent with renal biopsy findings in patients with AKI. This elevation in PARP1 expression might be attributed to trimethylation of histone H3 lysine 4 (H3K4me3). Furthermore, a reduction in PARylation levels mitigated renal dysfunction in the AKI mouse models. Mechanistically, liquid chromatography-mass spectrometry indicated that PARylation mainly occurred in receptor for activated C kinase 1 (RACK1), thereby facilitating its subsequent phosphorylation. Moreover, the phosphorylation of RACK1 enhanced its dimerization and accelerated the ubiquitination-mediated hypoxia inducible factor-1α (HIF-1α) degradation, thereby exacerbating kidney injury. Additionally, we identified a PARP1 proteolysis-targeting chimera (PROTAC), A19, as a PARP1 degrader that demonstrated superior protective effects against renal injury compared with PJ34, a previously identified PARP1 inhibitor. Collectively, both genetic and drug-based inhibition of PARylation mitigated kidney injury, indicating that the PARylated RACK1/HIF-1α axis could be a promising therapeutic target for AKI treatment.

Objective : To investigate the effect of high concentration of Caerulomycin A (Cae A) on HK2 in renal tubular epithelial cells and to explore the role of cytoplasmic nucleotide⁃binding oligomerization domain⁃like receptor protein 3 (NLRP3) in this process. Methods : The effect of different concentrations of Cae A on the viability of HK2 cells was determined by MTT; the expression of kidney injury molecule (KIM⁃1) and NLRP3 was detected by real⁃time quantitative PCR , Western blot and immunofluorescence , while the effect of Cae A on the mRNA expression of IL⁃1β , IL⁃18 , IL⁃33 , MCP⁃1 , TNF⁃α was also measured by real⁃time quantitative PCR. HK2 cells were divided into control group , high concentration of Cae A group and high concentration of Cae A plus NLRP3 inhibitor CY⁃09 group , and the expression of KIM⁃1 and NLRP3 protein was detected by Western blot. Results : The results of MTT showed that high concentration of Cae A could inhibit HK2 cell viability. Real⁃time quantitative PCR , Western blot and immunofluorescence assays showed that high concentration of Cae A upregulated the expression of KIM⁃1 and NLRP3 , as well as the mRNA levels of IL⁃1β , IL⁃18 , IL⁃33 , MCP⁃1 , TNF⁃α , while CY⁃09 could down⁃regulate the expression of NLRP3 and KIM⁃1. Conclusion High concentration of Cae A significantly inhibited the viability of HK2 cells and induced damage and inflammatory response to HK2 with some nephrotoxicity that might be achieved via NLRP3 pathway.